Two-stroke internal-combustion engine



Mafch c. s. JOHANSEN ETAL v 2,417,649

TWO STROKE INTERNAL COMBUSTION ENGINE Filed Aug. '22, 1945 rwve-k 'hs. Car-Z J. Joluanqen and Maya-n; R. G. Tease-n ratenied'lviar. lg, 1947 TWO-STROKE INTERNAL-CODIBUSTION ENGINE Car-l Steffen J ohansen and Mogens Roesdahl Groth Teisen, Copenhagen, Denmark Application August 22, 1945, Serial No. 611,942 In Denmark December 10, 1943 7 Claims. (01. 123-51) It is known that in two stroke internal combustion engines an advantage may be attained by letting two pistons work on one and the same combustion chamber or in other words byemploying two counter running pistons in one and the same cylinder, because it is then. possible to let one of the pistons control the exhaust and the otherjthe intake of the cylinder, so that a scavenging of the cylinder from one end to the other may be obtained.

It is known that in such motors it is advantageous to have a certain phase displacement between the pistons in order that the opening and the closing of the intake and exhaust ports should take place at the most advantageous moments. This phase displacement has for instance been obtained by mutually phase displacing two cranks, to which the two pistons are coupled by means of connecting rods and rocking levers.

The phase displacement obtained in this manner is, however, not altogether satisfactory, be cause it is also present in the neighbourhood of the inner dead centre, Where phase equality would in fact be preferable in order to obtain the best possible distribution of the power on the two pistons.

It has also been proposed to arrange an axia curve track at each end of the cylinder. Of course it is possible in thi manner to settle the phase relations of both pistons in any desired manner, because each piston is controlled by its own curve track independently of the other piston. This construction, however, is rather complicated and voluminous and. has not been successful.

According to the present invention it is possible to obtain the desired phase displacement by means of only one curve track, which renders possible a. substantially simplified-construction, and according to the invention this is obtained by interposing between the pistons and the guiding rollers contacting'with the curve track which is in this case in the form of a radial curve track or cam-rocking lever systems of such a kind, that in the neighbourhood of the inner dead centre approximate phase equality of the pistons is obtained, while inthe region of controlling the intake and exhaust ports a mutual phase displacement of the pistons is obtained.

Further details of the invention will appear from the following description with reference to the accompanying drawing showing a vertical cross section through a motor embodying the invention.

For the sake of clearness the illustration of the motor in the drawing is rather diagrammatic,

some details not necessary for the understanding,

of the invention being omitted-and other represented in a simplified form.

In the drawing I is a cylinder with two counter running pistons 2 and 3, The complete motor,

of course, may comprise any number of such cylinders, One of the pistons, the exhaust piston 2, controls the exhaust part4 of the cylinder, while the other piston, the intake piston 3 control the intake port 5. The spraying nozzl of the cylinder is represented at 6. To each of the pistons 2 and 3 is hinged a connecting rod 1 and fl-respectively, which at its remote end is rotatably connected with a rocking lever 9 and i0 respectively, that is rotatably mounted in the engine frame and at its free end carries a roller H and [2 respectively, preferably (not shown) in the form of a roller hearing, The rollers H and [2 contact from opposite sides with the outer surface of a common cam i3 fixed to the driving or output shaft of the motor, and they are held in constant contact with this cam by means of an auxiliary rocking lever I4 (only shown in the case of the rocking lever 9) that is torsionally connected with the rocking-lever 9 and I0 respectively and with a roller ll contacts with an auxiliary cam H3 fixed to the drivingshaft. The outer surface of the cam I3 is composed by a number of sections, each corresponding to a, cycle of the piston motion. In the example shown in the drawing the cam has four such sections, so that a full revolution of the cam and thereby of the driving shaft of the motor will correspond tofour cycles. In-

- stead of four sections the cam may have any other even number of sections, so that another transmission ratio is obtained,for instance 2:1, 6:1, etc.

. In the drawing it is seen that in the situation represented, where the pistons areat the inner .dead centre, the centre of rotation 25 of the rocking lever 9 is situated somewhat to the left of the centre 24 of the roller 1 I, or in other words the plane through the axis of rotation of the roller II and the axisof rotation of the "rocking lever 9 forms with the diametrical plans through the tangent line between the roller II and the cam l3 an angle a little smaller than This has the efiect that when the rocking lever moves, the point 24 will describe a circular are, which will substantially follow the horizontal diametrical line, until the rocking lever has rotated to the symmetrical position with respect to the vertical'plane through the axis of rotation of the rocking lever marked by the position 24' of the point 24. This corresponds, in the embodiment As long as the point 24 is situated 'between the shown position 24 and the point 24' the contact between the roller II and the cam l3 will substantially take place at the horizontal diametrical plane, and the same is the case with the contact between the roller l2 and the cam '13. Accordingly, the two rocking levers and thereby the two pistons will be substantially at equal phase. At the continued movement, however, when the cam l3 rotates in the direction of the arrow, the roller II will travel on the cam l3 against the direction of rotation, while at the same time the roller l2 travels on the cam IS in the direction of rotation. In other words, the angular distance between the rollers II and 12 as seen from the axis of the cam will vary, so that it will no longer amount to 180, as it did at the inner dead centre. This means that the rocking lever 9 and thereby the piston 2 are displaced in a forward direction, while the rocking lever l9 and the piston 3 are phase displaced in a backward direction. Accordingly, while at the inner dead centre and during the first 40% of the stroke approximate phase equality of the pistons will exist, a phase displacement of the exhaust piston in a forward direction and a phase displacement of the intake piston in a backward direction will occur in the remaining portion of the stroke. This phase displacement is maintained in the first part of the return stroke of the pistons and disappears only towards the inner dead centre of the pistons. In other words, it is obtained that the exhaust ports 4 are opened and closed before the intake ports, as desired, without this involving any phase inequality of the pistons in that part of the stroke, which is of special importance for the power development, viz. the part of the stroke in the neighbourhood of the inner dead centre. The value of the phase inequality and its situation in the stroke may be controlled ac-' cording to desire by displacing the point 23 in a horizontal and in a vertical direction respectively.

The embodiment of the motor shown in the drawing is very advantageous from a constructional point of view, seeing that full access to cylinders and pistons is attained by just removing the rocking levers from their bearings.

Having now particularly described and ascertained the nature of our invention and in what manner the same is to be performed we declare that what we claim is:

1. A two stroke internal combustion engine comprising two piston working in a common combustion chamber, a cam track for controlling the pistons and for producing rotary motion, leverages connected to said pistons and carrying guiding rollers having operative contact engagement with said cam track, the said leverages being constructed and positioned in such a manner that in the neighbourhood of the inner dead centre the pistons will be substantially at equal phase, while in the region of controlling the intake and exhaust ports a mutual phase displacement of the pistons will be present.

2. A two stroke internal combustion engine comprising two pistons working in a common combustion chamber, a cam track for controlling the pistons and for producing rotary motion, leverages connected to said pistons and carrying guiding rollers having operative contact engagement with said cam track, the said leverages being constructed and positioned in such a manner, that the angular distance between the guiding rollers as seen from the axis ofv the cam track will vary in the course of the stroke.

3. A two stroke internal combustion engine comprising two pistons working in a common combustion chamber, two rocking levers rotatably mounted in the engine frame at an intermediate point of their length, one end of each rocking lever being hingedly connected to one of the pistons by means of a connection rod, the other end of each rocking lever carrying a guiding roller, such guiding rollers contacting with the outer surface of one and the same radial cam track from opposite sides.

4. A two stroke internal combustion engine comprising two pistons working in a common combustion chamber, one of said pistons controlling the intake and the other piston controlling the exhaust of said combustion chamber, two rocking levers rotatably mounted in the engine frame at an intermediate point of their length one end of each rocking lever being hingedly connected to one of the pistons by means of a connection rod, the other end of each rocking lever carrying a guiding roller, such guiding rollers contacting with the outer surface of one and the same cam track from opposite sides.

5. A two stroke internal combustion engine comprising a cylinder having intake and exhaust ports, two counter running pistons operating in said cylinder, one of said pistons controlling the intake and the other piston controlling the exhaust ports of said cylinder, two rocking levers rotatably mounted in the engine frame at an intermediate point of their length, one end of each rocking lever being hingedly connected to one of the pistons by means of a connection rod, the other end of each rocking lever carrying a guiding roller, such guiding rollers contacting with the outer surface of one and the same cam track from opposite sides.

6. A two stroke internal combustion engine comprising two pistons working in a common combustion chamber, rocking levers coupled to said pistons and carrying rollers contacting with the outer surface of one and the same cam track from opposite sides, the rocking levers being mounted at points thus positioned that at the dead centre of the piston movement cycle the plane through the axis of rotation of a rocking lever and the axis of the roller mounted in the same will form an angle a little smaller than with the diametrical plane of the cam track through the tangent line between the roller and the cam track.

7. A two stroke internal combustion engine comprising a number of cylinders, two counter running pistons in each cylinder, a radial cam track belonging to each cylinder, a rocking lever coupled to each piston and carrying a guiding roller, the pair of guiding rollers belonging to pistons operating in one and the same cylinder contasting with the outer surface of the corresponding cam track from opposite sides.

The following references are of record in the" file of this patent:

UNITED STATES PATENTS Name Date Gray July 18, 1939 Number 

